How come the ScreenGUI and ImageLabel didn't pop up after onClicked?

When using UDim2 in a script, the arguments do not need {}'s like it shows in properties. UDim2.new(XScale, XOffset, YScale, YOffset) are the correct arguments.

Also, you need to place GUIs in the player's PlayerGui if you want them to be able to see the image. MouseClick has a parameter for the player who clicked the ClickDetector. Place the GUI in their PlayerGui.

local song1 = game.Workspace.BoxCD.song1
local gui = game.StarterGui
local screen = Instance.new("ScreenGui", gui)
local image = Instance.new("ImageLabel", screen)
touch = false

function onClicked(clicker) --clicker is the argument for the player who clicked the button
    if not touch then
        touch = true
        local screen = Instance.new("ScreenGui", clicker.PlayerGui) --Place the Gui inside their PlayerGui in order for them to see it.
        local image = Instance.new("ImageLabel", screen)
        image.Position = UDim2.new(0, 300, 0, 100) 
        image.Size = UDim2.new(0, 450, 0, 400)
        image.Image = "rbxassetid://238387775"
        touch = false
    end
end

script.Parent.ClickDetector.MouseClick:connect(onClicked)

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